Over the last two decades three-dimensional display technology has matured. Three-dimensional (3D) display devices add a third dimension (depth) to the viewing experience by providing each of the viewer's eyes with different views of the scene that is being watched.
As a result we now have various ways to view three-dimensional image/video signals. On the one hand we have glasses based three-dimensional display system where a user is presented with distinct images for her/his left eye and right eye. On the other hand we have auto-stereoscopic three-dimensional display systems that provide the un-aided eye of a viewer with a three-dimensional view of a scene.
In glasses-based systems the active/passive glasses provide a filter for separating the distinct images as presented on the screen for the respective eye of the viewer. In glasses-free or auto-stereoscopic systems the devices quite often are multi-view displays that use light directing means, e.g. in the form of a barrier or lenticular, to direct a left image to the left eye and a right image to the right eye
In order to provide content for use with stereoscopic multi-view display devices, various input formats have been designed over time. An example of such a format can be found in the published PCT application WO2006/137000(A1). This document discloses an image exchange format for image and depth information in combination with further information such as depth and/or occlusion depth. Information provided in this manner may be used to render images for use with auto-stereoscopic multi-view displays based on lenticular or barrier technology.
The article “Synthesis of multi viewpoint images at non-intermediate positions” by P. A. Redert, E. A. Hendriks, and J. Biemond, in Proceedings of International Conference on Acoustics, Speech, and Signal Processing, Vol. IV, ISBN 0-8186-7919-0, pages 2749-2752, IEEE Computer Society, Los Alamitos, Calif., 1997 discloses a method of extracting depth information and of rendering a multi-view image on basis of the input image and the depth map.
In order to improve the results of the aforementioned image based rendering techniques various techniques have been devised that make use of additional occlusion texture and occlusion depth as disclosed in WO2006/137000(A1). The addition of an occlusion texture and an occlusion depth map however are relatively costly in that it may require the transmission of an additional image and depth map for use in rendering.
Apart from adding additional image data in the form of further image and depth maps, it is also known that additional metadata can be provided in order to improve the quality of the image based rendering. An example of such metadata is provided in PCT application WO2011/039679 (A1). This document discloses a method of encoding a video data signal providing a preferred rendering direction indicator for use in rendering further views.